No residual adult T2D risk for boys who achieved normal weight by 13

Weight loss in childhood appears to eliminate the legacy effect of early overweight on adult-onset type 2 diabetes risk, a large population-based longitudinal study showed.

Boys who returned to normal weight by age 13 had a risk of type 2 diabetes at age 30 to 60 similar to those never overweight in the first place (hazard ratio 0.96, 95% CI 0.75-1.21), reported Lise G. Bjerregaard, PhD, of Bispebjerg and Frederiksberg Hospital in Denmark, and colleagues in the New England Journal of Medicine.

"I was surprised that men who had been overweight at 7 years of age, but normalized their weight by age 13 years and were normal weight as young men, had such a similar risk of type 2 diabetes as men who were never overweight," Bjerregaard explained to MedPage Today. "I expected that they could reduce their risk, but not as completely as they did."

Overall, and not surprisingly, the group found that men who had been overweight at ages 7 and 13 had a higher risk for adult-onset type 2 diabetes compared with those who had no history of being overweight (HR 1.47, 95% CI 1.10-1.98). This risk was elevated even among boys who were of normal weight at age 7 but overweight by age 13 (HR 1.73, 95% CI 1.38-2.16).

Men who were persistently overweight from childhood through early adulthood saw the highest risk for developing type 2 diabetes:

HR 4.14, 95% CI 3.57-4.79; starting at 7 years of age

HR 4.20, 95% CI 3.62-4.88; starting at 13 years of age

"Our findings suggest that weight loss from childhood to early adulthood can reduce the increased risks of type 2 diabetes among overweight and obese boys," said Bjerregaard. "In particular, boys who lose weight before age 13 years and maintain normal weight until early adulthood will reduce their risk to the same levels as among normal weight."

Bjerregaard added that if "boys are still overweight or obese at age 13 years, and then lose weight before early adulthood, their risks of later type 2 diabetes will only be partly reduced," and stressed the importance of prevention in early childhood, "especially before puberty, as this may greatly reduce the risks of type 2 diabetes later in life."

The study included 62,565 Danish men, 10.7% of whom developed type 2 diabetes during the 1,969,165 person-years follow-up period. Defined using the CDC's criteria for overweight -- BMI ≥17.38 at age 7, ≥21.82 at age 13, and ≥25 in early adulthood -- 5.4% of the boys in the study were considered overweight at age 7, 5.5% were overweight at age 13, and 8.2% were overweight in early adulthood. Only around 1.6% of men were overweight at all ages.

Although not as strong, presence of overweight in early life was also linked to a higher risk of developing type 2 diabetes much later in life -- from ages 60 to 76. Similar patterns were reflected, with diabetes risk reversed if the individual returned to normal weight before age 13 (HR 0.81, 95% CI 0.62-1.07). The highest risk for later-life diabetes was seen in those overweight at both age 13 and early adulthood (HR 2.81, 95% CI 2.24-3.53).

Inclusion of intelligence-test scores and levels of education did not have any significant modification on the relationships reported (P>0.79 for all interactions).

Regardless of their childhood weight, men who were obese in early adulthood (BMI percentile ≥95th) had a very high risk of developing type 2 diabetes from ages 30 to 60 (HR 6.19-8.74 across BMI percentiles at age 7). However, men who were obese at any time point were able to cut their risk of type 2 diabetes in adulthood in half by reducing their BMI to overweight status.

Despite the large sample size of the study, the lack of later-life BMI data may limit the findings, although the researchers noted this variable was likely "a mediator rather than a confounder."

The study was supported by funding from the European Commission Horizon 2020 program as part of the DynaHEALTH project, and by the European Research Council.

Bjerregaard and one co-author reported grants from the European Union's Horizon 2020 Research and Innovation Programme during the conduct of the study.

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